What is the smallest particle of a compound called?

The smallest particle of a compound is referred to as a molecule. A molecule is formed when two or more atoms chemically bond together. It represents the lowest level of a structure that retains the chemical properties of that compound. For example, a water molecule (H2O) consists of two hydrogen atoms and one oxygen atom bonded together, which collectively exhibit the characteristics that define water.

In contrast, atoms are the basic units of matter and the building blocks of molecules. While atoms can exist independently, when they bond together in specific arrangements, they form molecules that represent compounds. A formula unit typically describes the simplest ratio of ions in an ionic compound and is used primarily for ionic compounds rather than covalent ones that form molecules. Elements refer to pure substances consisting of only one type of atom and do not represent compounds at all.

Thus, identifying a molecule as the smallest particle of a compound accurately captures its ability to maintain the chemical identity and properties of that compound.